light

• light can be: reflected, refracted, and diffracted
• refractive index (n) = speed of light in air / speed of light in a medium
• n = sin θi / sin θr
• application total internal reflection:

  1. periscope
  2. optical fibre
• reflection of light: the light emit from the objects hits the mirror & reflects back
• properties of the image form:

  1. same distance from mirror
  2. latterly inverted
  3. same size
  4. upright
  5. virtual
• focal point is the point in the center line of the lens where the parallel light rays bend
• focal length is the distance between the focus point & center of the lens
• 1. when object is close to F: real, inverted, magnified, far from lens
  2. when object is far from F: closer to lens, inverted, real, diminished
  3. when object is close to lens: magnified, upright, virtual
• defects of vision:

  1. long sight: a person who can see a distant object clearly but cannot see near object
  2. short sight: a person who can see near objects clearly but not distant objects
• long sight: image formed behind retina - solve with convex lens

  short sight: image formed in front of retina - solve with concave lens